The field of the disclosure relates generally to electromagnetic actuators and, more particularly, to an electromagnetic actuator with multiple air gaps and pole shaping and a method of use.
Most known electromagnetic actuators convert electric power into magnetic force to move a push pin. The push pin is coupled to a plunger that moves freely within a cavity in the actuator, generally within a guiding structure. Current passes through a coil in the electromagnetic actuator and generates an electromagnetic field and, more specifically, an electromagnetic flux.
For many of these known electromagnetic actuators, certain surfaces of the plunger operate as poles that are attracted to the electromagnetic flux, pulling the plunger toward the coil. A flux circuit is formed around the coil by the plunger, the poles, and a yoke. An air gap between the poles and the yoke dictates the magnetic force with which the plunger is pulled toward the coil. The air gap is a region of high magnetic reluctance, which can be air, a vacuum, or another non-magnetic material. The push pin transfers the magnetic force to an external object. When the plunger reaches a stable position, the plunger is latched in place by one or more permanent magnets.
Such known electromagnetic actuators often replace mechanical spring mechanisms in various applications. A force-stroke relationship, which is frequently represented as a force-stroke curve, for a spring does not always meet the requirements of a given application, for example, and without limitation, a vacuum circuit breaker. Electromagnetic actuators have a force-stroke relationship that matches the mechanical characteristics of vacuum circuit breakers. Electromagnetic actuators are also available at a lower cost, require less maintenance, have a reduced footprint, and greater endurance. However, certain applications, e.g., certain vacuum circuit breakers, call for unique force-stroke relationships depending on the stroke direction. For vacuum circuit breakers, a closing force-stroke curve and an opening force-stroke curve are often different. Additionally, some vacuum circuit breakers also utilize a spring effect of the contacts themselves to achieve a desired force-stroke curve.